Disclaimer: This information is not a substitute for professional medical advice, diagnosis or treatment.
Clinically reviewed by Dr James Harris, MBBS, FRACGP
AHPRA: MED0000981120
Shiga toxin-producing Escherichia coli (STEC) is a group of bacteria that can cause severe gastrointestinal illness in humans. While many strains of E. coli are harmless and live naturally in the intestines of people and animals, STEC strains produce toxins that can damage the lining of the intestine and, in some cases, lead to serious complications affecting the kidneys.
STEC infections are often associated with contaminated food, but many people are unaware that animals, particularly cattle and other farm animals, are one of the primary reservoirs for these bacteria. Understanding how STEC spreads and how to reduce your risk can help protect you and your family.
What is STEC?
STEC stands for Shiga toxin-producing Escherichia coli. These bacteria produce toxins known as Shiga toxins, which can cause inflammation and damage in the digestive tract. The best-known STEC strain is E. coli O157:H7, although many non-O157 strains can also cause illness.
Farm animals, particularly cattle, sheep, goats, and deer, commonly carry STEC in their intestines without appearing sick. The bacteria are shed in animal faeces and can contaminate food, water, soil, and surfaces.
Quick Answer: How do humans get STEC?
People usually contract STEC by:
- Eating contaminated food, especially undercooked beef and raw produce.
- Drinking unpasteurised milk, juice, or contaminated water.
- Touching infected animals or contaminated environments and then touching their mouth.
- Having close contact with an infected person.
What are the symptoms of STEC infection?
Symptoms typically develop 3 to 4 days after exposure, although they can appear anywhere from 1 to 10 days after infection.
Common symptoms include:
1. Diarrhoea: Diarrhoea is the most common symptom and may become bloody as the infection progresses.
2. Severe Stomach Cramps: Many people experience significant abdominal pain and cramping.
3. Nausea and Vomiting: Nausea and vomiting can occur and may contribute to dehydration.
4. Mild Fever: A fever may occur but is usually low-grade or absent.
Most people recover within a week, but some develop serious complications that require urgent medical attention.
A serious complication: Haemolytic Uraemic Syndrome (HUS)
A small proportion of STEC infections progress to haemolytic uraemic syndrome (HUS), a potentially life-threatening condition that can damage red blood cells and cause kidney failure.
Warning signs of HUS include:
- Reduced urination
- Bloody urine
- Extreme fatigue
- Unusual bruising
- Pale skin
- Drowsiness or lethargy
Children under five years of age are at the highest risk of developing HUS, although it can occur in adults.
How STEC spreads from animals to humans
Direct contact with farm animals
Cattle are considered the main source of STEC infections in humans. People can become infected by touching animals or contaminated surfaces in places such as:
- Farms
- Agricultural shows
- Petting zoos
- Wildlife parks
- Livestock yards
Even healthy-looking animals can carry STEC and shed it in their faeces.
Contaminated foods
Animal faeces can contaminate meat during processing or spread to crops through contaminated soil, water, or fertiliser. Foods commonly linked to STEC outbreaks include:
- Undercooked beef
- Raw milk
- Unpasteurised dairy products
- Leafy greens
- Sprouts
- Fresh produce
Contaminated water
Water sources may become contaminated by animal waste runoff. Infection can occur through:
- Drinking untreated water
- Accidentally swallowing water while swimming in lakes, rivers, or dams
- Consuming food washed in contaminated water
How to reduce your risk of STEC infection
Wash hands thoroughly
Wash hands with soap and running water:
- After touching animals
- After visiting farms or petting zoos
- Before eating or preparing food
- After using the toilet
- After changing nappies
Cook meat properly
Ground and minced beef products should be cooked thoroughly to kill harmful bacteria. Avoid consuming raw or undercooked meat.
Choose pasteurised products
Drink only pasteurised milk and consume pasteurised dairy products and juices whenever possible.
Wash fresh produce
Rinse fruits and vegetables under running water before eating or preparing them, especially if consuming them raw.
Prevent cross-contamination
Keep raw meat separate from ready-to-eat foods and use separate cutting boards and utensils when preparing food.
Avoid untreated water
Take care around and avoid drinking untreated water. Try not to swallow water while swimming in natural waterways.
When should you see a doctor?
Seek medical attention if you experience:
- Bloody diarrhoea
- Severe abdominal pain
- Signs of dehydration
- Symptoms lasting longer than a few days
- Reduced urination or other signs of HUS
Young children, older adults, pregnant women, and people with weakened immune systems should seek medical advice promptly if they develop symptoms.
Frequently asked questions
How do people get STEC infection?
People can become infected by:
- Eating contaminated food, particularly undercooked beef
- Drinking contaminated water
- Consuming unpasteurised milk or dairy products
- Touching infected animals or contaminated environments
- Having close contact with someone who is infected
Farm animals such as cattle, sheep, goats, and deer are common carriers of STEC.
Can you catch STEC from animals?
Yes. Animals can carry STEC bacteria without appearing sick. People can become infected after touching animals, animal faeces, contaminated fencing or equipment, or surfaces in environments such as farms, petting zoos, and agricultural shows. Proper handwashing after animal contact is essential.
What are the first symptoms of STEC infection?
Symptoms usually begin 3 to 4 days after exposure and commonly include:
- Diarrhoea, which may become bloody
- Severe stomach cramps
- Nausea
- Vomiting
- Mild fever or no fever
Most people recover within a week, although some develop serious complications.
How is STEC diagnosed?
STEC is typically diagnosed through a stool test. The laboratory can identify whether STEC bacteria are present and, in some cases, determine the specific strain responsible for the infection. Additional blood and urine tests may be required if complications are suspected
How is STEC treated?
Treatment generally focuses on supportive care, including:
- Drinking plenty of fluids
- Oral rehydration solutions
- Rest
- Hospital treatment if dehydration becomes severe
There is no specific medication that cures STEC infection, and most people recover without antibiotics.
Are antibiotics used to treat STEC?
Antibiotics are generally not recommended for STEC infections. Healthcare professionals will determine the most appropriate treatment based on the individual’s condition.
Should I take anti-diarrhoea medication if I have STEC?
Anti-diarrhoeal medicines are usually not recommended unless specifically advised by a healthcare professional. Slowing bowel movements may increase the time toxins remain in the intestines and could increase the risk of complications.
What is haemolytic uraemic syndrome (HUS)?
HUS is a serious complication that can occur after STEC infection. It can cause:
- Kidney failure
- Destruction of red blood cells
- Low platelet counts
It is most common in children under five years of age and requires urgent medical treatment.
Who is most at risk of severe STEC infection?
People at higher risk include:
- Children under 5 years
- Older adults
- Pregnant women
- People with weakened immune systems
These groups are more likely to experience severe illness or complications.
How long does STEC infection last?
Most people recover within 5 to 10 days. However, symptoms can vary in severity, and some individuals may require hospital treatment if complications develop.
How can I reduce my risk of STEC infection?
You can reduce your risk by:
- Washing hands thoroughly after touching animals
- Cooking meat thoroughly
- Avoiding unpasteurised milk and dairy products
- Washing fruits and vegetables before eating
- Preventing cross-contamination during food preparation
- Avoiding untreated water
These simple food safety and hygiene measures are highly effective at preventing infection.
Can STEC spread from person to person?
Yes. STEC can spread through person-to-person contact, particularly in households, childcare settings, and aged care facilities. Good hand hygiene is one of the most effective ways to prevent transmission.
Is STEC infection common in Australia?
Yes. Around 1,000 STEC infections are reported in Australia each year. Most cases are sporadic, but outbreaks can occur, particularly when contaminated food products enter the food supply chain.
Key takeaway
STEC is a potentially serious bacterial infection that commonly originates from livestock such as cattle, sheep, and goats. It can spread through contaminated food, water, animal contact, and person-to-person transmission. While most people recover within a week, some develop serious complications, including kidney damage. Good hand hygiene, safe food handling, thorough cooking, and avoiding unpasteurised products are among the most effective ways to reduce your risk.
References
- Australian Centre for Disease Control. Shiga toxin-producing Escherichia coli (STEC) infection and haemolytic uraemic syndrome (HUS).
- European Centre for Disease Prevention and Control. Shiga toxin-producing Escherichia coli (STEC).
- California Department of Public Health. STEC Infection Information.